Compositions for waving of hair contain a reducing agent for breaking the disulfide bonds in hair, thereby allowing the hair to be permanently reshaped. U.S. Pat. No. 4,158,704, for example, teaches methods for waving of hair using compositions containing thioglycolate compounds as the reducing agents. U.S. Pat. No. 5,554,364 teaches that thioglycolate compositions produce waving of hair that typically lasts about 2 to 4 months. However, mercaptans or thioglycolates produce a strong unpleasant odor.
U.S. Pat. No. 5,338,540 teaches hair waving compositions containing a sulfite and/or bisulfite reducing system, urea, and a cationic polyquaternary resin, which yield a hair waving or straightening effect equivalent to thioglycolate compositions, but without the unpleasant odors associated with thioglycolate. However, U.S. Pat. No. 5,474,578 teaches that bisulfites are known to strip color from artificially colored hair.